Hi, I have something very similar going on. I'm on 7-8 110/25 sinemet + 3-4 entacapone a day -dependant on sleep issues. I have no answers about this only 2 observations. While sinemet always had a sleepy side effect for me it wasn't this extreme. When I was treated aggressively for b12 deficiency this effect of sinemet disappeared and my offs and ons became clear. Sadly not happening now, I'm on bi-monthly shots and am due one now - have just awaken from an intermittently sleepy patch of weel over two hours, it's doing my head in, it's only 11.30 am.